To study in vivo and in vitro including tissue culture of cerebral arteries, the effect of prostaglandin synthesis and inhibition on cerebral blood flow, vasospasm, arterial reactivity and ischemia in normal animals and animals with induced stroke related states. To study and refine knowledge of the extracranial-intracranial vasa vasorum in humans and animals relating to fibrous dysplasia vascular repair and reactivity and microsurgical technique. To develop a model of spontaneously occurring intracranial aneurysm which is identifiable by arteriography and frequent in production. To study altered vascular permeability in spinal fluid and sera of diabetics. To initiate clinical regimens to prevent cerebrovasospasm and improvement of medical therapy of occlusive stroke. To determine why platelets are hyporesponsive in vitro in certain patients with stroke and transient ischemic attacks.